How do we get rid of the pesky mold?

My Grandmother started growing wheatgrass in early 1976. She was in
her late 50's then. She eventually quit growing it a year ago due to
the mold and the bad effects she was getting due to the mold. Let me
just say she is now nearing 86 and she lives in her own home, walks
to get her own groceries, is on absolutely NO medications. She never
has been. She has all her mental faculties. Sure she has great DNA
but she swears it's directly due to her wheatgrass. She has taken
some major spills in the last year and has broke nothing but her
nose. That particular fall she fell on her face. It was very bad
but she experienced absolutely no pain and her healing was in record
time. She is a stong little lady.

Now she is having great problems with a layer of fuzzy mold on the
trays she now grows. It is causing her great angst. She is doing
nothing different. She has tried using kelp. She's put it in the
soil several different ways...she's tried it in the water. it has
lessened the mold a bit but it's still there. I have read that some
use grapefruit seed extract (what form, how much?), Azomite (what is
it and what form and how much?), and the kelp. Can anybody instruct
me so I can help her and then we both can grow it and enjoy the
effects for years to come. We live in Calgary, Alberta Canada.

We appreciate any and all hints as we do not want to be reduced to
buy the frozen juice 10 X 1oz. trays for $17.99. That is roughly $60
for a one month supply if you only take 1 oz. per day, per person.
Growing it ourselves would be so much more economical.

thank you in advance for all helpful replies.

Kim